Category: SMB/NetBIOS

This is a technical rundown of a vulnerability that we’ve dubbed “WebExec”. The summary is: a flaw in WebEx’s WebexUpdateService allows anyone with a login to the Windows system where WebEx is installed to run SYSTEM-level code remotely. That’s right: this client-side application that doesn’t listen on any ports is actually vulnerable to remote code execution! A local or domain account will work, making this a powerful way to pivot through networks until it’s patched.

High level details and FAQ at https://webexec.org! Below is a technical writeup of how we found the bug and how it works.

Thanks to a Google Alert on my name, I recently found Laurent Gaffié’s blog post about MS10-006 (Microsoft Technet link).

Posts in this series (I’ll add links as they’re written):

1. What does smb-psexec do?
2. Sample configurations ("sample.lua")
3. <a href=/blog/?p=404'>Default configuration ("default.lua")</a>
4. Advanced configuration ("pwdump.lua" and "backdoor.lua")

Posts in this series (I’ll add links as they’re written):

1. What does smb-psexec do?
2. Sample configurations ("sample.lua")
3. Default configuration ("default.lua")
4. Advanced configuration ("pwdump.lua" and "backdoor.lua")

Posts in this series (I’ll add links as they’re written):

1. What does smb-psexec do?
2. Sample configurations ("sample.lua")
3. Default configuration ("default.lua")
4. Advanced configuration ("pwdump.lua" and "backdoor.lua")

Greetings everybody!

I spent a good part of the past month traveling, which meant staying in several hotels, both planned and unplanned. There’s nothing like having a canceled flight and spending a boring night in San Francisco! But hey, why be bored when you have a packet sniffer installed? :)

Hello once again!

I just finished updating my smb-check-vulns.nse Nmap script to check for the recent SMBv2 vulnerability, which had a proof-of-concept posted on full-disclosure.

WARNING: This script will cause vulnerable systems to bluescreen and restart. Do NOT run this in a production environment, unless you like angry phonecalls. You have been warned!

Hey all,

For my SANS GPEN Gold certification (first Gold-certified analyst for GPEN – go me!) I wrote a paper on my SMB scripts for Nmap. The paper is titled “Scanning Windows Deeper With the Nmap Scanning Engine”. I started writing it a few months ago, and collaborated with Fyodor in the early stages. Hopefully it’s a useful guide!

I talk a bit about the theory and protocols behind the scripts, then dive into a few of the more interesting ones and talk about how they work and how they can be used.

Let me know what you think!

Hey all,

With the upcoming release of Nmap 4.85, Brandon Enright posted some comments on random Nmap thoughts. One of the things he pointed out was that people hadn’t heard of nbstat.nse! Since I love showing off what I write, this blog was in order.

Morning, all!

Last night Fyodor and crew rolled out Nmap 4.85beta7. This was because some folks from the Honeynet Project discovered a false negative (showed no infection where an infection was present), which was then confirmed by Tenable. We decided to be on the safe side, and updated our checks.

I’m going to start off this blog by wishing a happy birthday to a very important person – me. :)

Now, onto the content!

PsTools is a suite of tools developed by Sysinternals (now Microsoft). They’re a great complement to any pen test, and many of my Nmap scripts are loosely based on them. As good as they are, they aren’t without their quirks!

Here are a few topics worth discussing:

• Ports and traffic
• Specifying an account
• Running it purely in a console

Most (possibly all) of the PsTools use standard Windows functions. That makes life easy – we can expect PsTools to act the same way other remote functions work. If we know how!

Using Nmap to scan for the famous Conficker worm.

Today, I’m going to share some knowledge and techniques on bruteforcing Windows passwords. Hopefully, some of you have thought about this and can give me even more advice. If you know anything, post it!

Today I want to discuss how the pwdump6 and fgdump tools work, in detail, and how I was able to integrate pwdump6 into my Nmap scripts. Is this integration useful? Maybe or maybe not, but it was definitely an interesting problem.

Hi everybody,

I spent most of last Saturday exploring how SysInternals’ PsList program works, and how I could re-implement it as an Nmap script. I quickly discovered that the HKEY_PERFORMANCE_DATA (HKPD) registry hive was opened, then it got complicated. So I went digging for documentation and discovered a couple journals posts written by Microsoft’s Matt Pietrek wrote back in 1996. Those led me to the WinPerf.h header file. The three of those together were enough to get this working.

Microsoft released ms08-068 this week, which fixes a vulnerability that’s been present and documented since 2001. I’m going to write a quick overview of it here, although you’ll probably get a better one by reading The Metasploit Blog.

Hi everybody!

This is going to be a fairly high level discussion on the sequence of calls and packets required to make MSRPC calls over the SMB protocol. I’ve learned this from a combination of reading the book Implementing CIFS, watching other tools do their stuff with Wireshark, and plain ol’ guessing/checking.

Hello everybody!

Lately I’ve been putting a lot of work into Nmap scripts that’ll probe Windows deeply for information. I’m testing this with both authenticated and unauthenticated users, mostly to determine how well error conditions are handled. Every once in awhile, however, I notice something that the anonymous account or guest account can access that seems odd. And today, I felt like I ought to post a blog, so you get to hear about it!

How synced up are the clocks on your servers? Ignoring your system times may give an important clue to attackers. Read on to find out more!

As you can see from my past few posts, I’ve been working on implementing an SMB client in C. Once I got that into a stable state, I decided to pursue the second part of my goal for a bit – porting that code over to an Nmap script. Never having used Lua before, this was a little intimidating. So, to get my feet wet, I modified an existing script – netbios-smb-os-discovery.nse – to have a little bit of extra functionality:

Last post, I promised I’d post about NTLMv2 once I got it implemented. And, here we are.

The LMv2 and NTLMv2 responses are a little bit trickier than the first versions, although most of my trouble was trying to figure out how to use HMAC-MD5 in OpenSSL. The good news is that LMv2 and NTLMv2 are almost identical to each other, with only one minor difference.

As I’m sure you’ve noticed with my first two posts, my NetBIOS/SMB project is taking up most of my time. I hit a bump this weekend, and almost got to the point where the only valid answer was throwing things; luckily, however, I figured it out. I did make a new enemy, though: signed data types! The devil’s datatype.

My current project, as you can see by my last post, is to learn how to work in Microsoft’s networking protocols (NetBIOS, SMB, CIFS, etc). This is obviously difficult due to the lack of standards and documentation, but there are two things that are seriously making my life difficult:

All right, maybe 0.02 doesn’t sound so impressive, but I’ve put a lot of work into it so eh?

Anyway, I just finished putting together nbtool 0.02. It is partly a test program for myself, and partly a handy tool for probing NetBIOS networks. Here is a link to the tool itself (I’ve tested this on Linux, OS X (ppc + intel), iPhones, and Windows (cygwin)): http://www.skullsecurity.org/wiki/index.php/Nbtool